Portable wireless communication devices, such as wireless microphones, wireless audio transmitters, wireless audio receivers, and wireless earphones, include antennas for communicating radio frequency (RF) signals without the need for a physical cable. The RF signals can include digital or analog signals, such as modulated audio signals, data signals, and/or control signals. Portable wireless communication devices are used for many functions, including, for example, enabling broadcasters and other video programming networks to perform electronic news gathering (ENG) activities at locations in the field and the broadcasting of live sports events. Portable wireless communication devices are also used by, for example, stage performers, singers, and/or actors in theaters, music venues, and film studios, and public speakers at conventions, corporate events, houses of worship, schools, and sporting events.
One common type of portable wireless communication device is a wireless bodypack microphone transmitter, which is typically secured on the body of a user (e.g., with belt clips, straps, tape, etc.) and is in communication with a wireless microphone (such as, e.g., a handheld unit, a body-worn device, or an in-ear monitor) and a remote receiver (e.g., an audio amplifier or recording device). Another common type of portable wireless communication device is a wireless bodypack personal monitor receiver, which is also typically secured on the body of the user (e.g., with belt clips, straps, tape, etc.) and is in communication with wireless earphones or other personal monitor (e.g., in-ear monitor, headphones or other headset) and a remote transmitter (e.g., an audio source).
The antennas included in the portable wireless communication devices can be designed to operate in certain spectrum band(s), and may be designed to cover either a discrete set of frequencies within the spectrum band or an entire range of frequencies in the band. The spectrum band in which a portable wireless communication device operates can determine which technical rules and/or government regulations apply to that device.
For example, the Federal Communications Commission (FCC) allows the use of wireless microphones on a licensed and unlicensed basis, depending on the spectrum band. Most wireless microphone systems that operate today use spectrum within the “Ultra High Frequency” (UHF) bands that are currently designated for television (TV) (e.g., TV channels 2 to 51, except channel 37). Currently, wireless microphone users need a license from the FCC in order to operate in the UHF/TV bands (e.g., 470-698 MHz). However, the amount of spectrum in the TV bands available for wireless microphones is set to decrease once the FCC conducts the Broadcast Television Incentive Auction. This Auction will repurpose a portion of the TV band spectrum—the 600 MHz—for new wireless services, making this band no longer available for wireless microphone use. Wireless microphone systems can also be designed for operation in the currently licensed “Very High Frequency” (VHF) bands, which cover the 30-300 MHz range.
An increasing number of wireless microphone systems are being developed for operation in other spectrum bands on an unlicensed basis, including, for example, the 902-928 MHz band, the 1920-1930 MHz band (i.e. the 1.9 GHz or “DECT” band; also included within the 1.8 GHz band), and the 2.4-2.483 GHz band (i.e. “ZigBee” or IEEE 802.15.4; referred to herein as the “2.4 GHz band”). However, given the vast difference in frequency between, for example, the UHF/TV bands and the ZigBee band, wireless microphone systems that are specifically designed for one of these two spectrums typically cannot be repurposed for the other spectrum without replacing the existing antenna(s).
Moreover, antenna design considerations can limit the number of antennas that are included within a single device (e.g., due to a lack of available space), while aesthetic design considerations can restrict the type of antennas that can be used. For example, wireless bodypack transmitters and/or receivers typically include a reduced-size antenna that is at least partially integrated into the bodypack housing to keep the overall package size small and comfortable to use or wear. However, this limitation in antenna size/space makes it difficult for the wireless bodypack device to provide sufficient radiated efficiency and broadband antenna coverage.
Accordingly, there is a need for a wireless bodypack device that can adapt to changes in spectrum availability, but still provide consistent, high quality, broadband performance with a low-cost, aesthetically-pleasing design.